The present invention relates to a foundation unit of structural objects such as a retaining wall (a dry-walled retaining wall, an L-shaped retaining wall, etc.), upper and lower boundaries of retaining walls, and a structure for preventing sliding of retaining walls.
As one mode of a retaining wall, there is that which is formed by disposing a foundation unit on a ground and fixedly installing a retaining wall unit on the foundation unit.
In such a retaining wall, a sliding force caused by a horizontal external force such as an earth pressure is counteracted by a shear resistance (ΣV×tan φ) occurring between the lower surface of the foundation unit and the top surface of the ground. Thus, generally, the width of the foundation unit is appropriately calculated to secure the safety.
Then, when it is postulated such that “a rigid ground or base rock is provided, or the adhesion with the surrounding grounds is to be secured without disturbing the ground”, and in under this condition, a protruding sliding resistive element is arranged on the lower surface of the foundation unit. In this way, it may become possible to respond to a construction site where the width of the foundation unit cannot be widened.
For example, there is a prior technology such that on the lower surface of a basement, which is a foundation unit of an L-shaped retaining wall, a separately-formed sliding resistive element is installed consecutively to implement sliding prevention of the retaining wall (for example, see Patent Document 1). That is, when constructing such an L-shaped retaining wall, a groove for embedding the sliding resistive element is excavated to be formed on the ground, and the sliding resistive element that is previously formed as a precast concrete is fit and placed into that groove. In this way, the sliding resistive element is integrally installed consecutively of the basement of the L-shaped retaining wall.
At this time, in the groove for embedding the sliding resistive element, a part of the ground is excavated so as to prepare a size that can facilitate fitting of the sliding resistive element therein, and after placing the sliding resistive element in the groove, a filling material such as crushed stone is filled in a gap formed between front and back walls of the groove and the sliding resistive element.
In this way, the sliding resistive element is caused to exert a passive earth pressure thereby to increase the sliding resistance of the retaining wall.
Moreover, at a retaining wall unit formed by stacking one above another a plurality of retaining wall blocks on the foundation unit, a pair of left and right rod-shaped slide preventive pieces are upwardly projected in left and right side portions of an upper-end surface front portion of the foundation unit, and left and right side portions of a front-wall lower portion of the retaining wall block forming the lowest level is caused to touch the both slide preventive pieces, thereby preventing the retaining wall block from sliding forwardly.
Moreover, also in left and right side portions of an upper-end-surface front portion of each retaining wall block, a pair of left and right rod-shaped slide preventive pieces are upwardly projected, and the left and right side portions of the front-wall lower portion of the retaining wall block adjacent to the upper level are caused to touch the both slide preventive pieces. In this way, forward sliding of each retaining wall block is prevented (for example, see Patent Document 2).
Patent Document 1: Japanese Patent No. 2669797
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-204669